A Catholic high school increased security Monday after an unspecified threat was discovered on the social networking Web site, MySpace.com, the school announced.

All but three entrances at Holy Trinity High School in Hicksville were to be locked, with Nassau County police officers posted at each entrance, the Long Island school said in a notice on its Web site.

Police were not releasing details of the threat because the investigation was ongoing, said spokeswoman Officer Jean DeLuca.

The threat was made "through communications taking place on the MySpace.com Web site" and was scheduled to occur on Monday, according to the school announcement.

It was expected that the school day would be uninterrupted, except for delays entering the building, the message said.

Myspace.com is owned by News Corp., the parent company of FOXNews.com.